I need to run a 3" PVC downspout to the street. The issue is that the only place I have to run it is down my gravel driveway. At the house, the downspout is at least 12in below the surface of the ground. From what I understand, if using schedule 40 pipe that would be deep enough to protect it.

The issue is that the driveway slopes down and by the time the pipe would reach the concrete sidewalk it would be only 3 to 4 inches underground. Even with schedule 40 pipe, I believe that would get crushed by a car.

With a schedule 40 pipe 3 to 4 inches underground how should it be protected against being crushed by a car?

If your driveway isn't ridiculously long you can eat the price difference and run schedule 80 instead. That gets you quite a bit more crush strength in large diameters, and the OD is the same so it's simple to transition.
– Matthew GauthierAug 28 '18 at 0:40

@MatthewGauthier Thanks, didn't even know schedule 80 existed. It's only about 20 feet from the house to the sidewalk. I looked up the prices and that's very doable.
– vini_iAug 28 '18 at 10:09

1 Answer
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I'd be surprised if the pipe was crushed by a typical car. Very heavy pickups or SUVs, maybe. PVC is surprisingly tough.

However, you could scrape away the gravel to the level of the pipe to a width of 8-10 inches and lay some treated two-by lumber or steel plate over the pipe, resting on the adjacent gravel. You could drive some large pole barn nails through the edges of the lumber (after drilling appropriately-sized holes) to keep it in position if your gravel tends to be loose. Cover again with gravel and be happy.